Alessandro Sozza
University of Turin, Italy

Nutrient uptake by marine microorganisms

We investigate the nutrient uptake of absorbing particles in a fluid flow, by means of direct numerical simulations. The nutrient is advected according to Navier-Stokes equation and is depleted in the location of the particles. We consider the sink term linearly proportional to the nutrient concentration. This is also motivated by the fact that nutrient resources in the ocean are typically limited. Coupling between nutrient field and absorbing particles is designed using a immersed boundary method. The uptake of each cell is obtained by integrating the instantaneous uptake along the cell trajectory. In this talk I will present some preliminary results using simple flows and configurations of particles, in order to test the uptake response. I will discuss two aspects that may influence the uptake. Diffusive interactions between particles may shield part of the flux and be disadvantageous for the uptake of the single cell. On the contrary, advection of the fluid flows (from simple shear to turbulence) is usually found to enhance the flux into the cell.